It's somewhat of a mystery on whether or not Kate Upton got a boob job. It's hard to find any good before and after pictures of her alleged plastic surgery because she would have gotten it before gaining stardom. The supermodel is listed at 5' 10" with a bra size of 34D. At first glance, it looks like she should have a DD though.
It's hard to say for sure if Kate Upton has gotten breast implants. This before and after picture makes it look like her bust is much smaller to the left, but it could just be attributed to the dress she's wearing. The blue dress is baggy and loose fitting while the white / cream top is tight.
Kate Upton's cleavage looks much more pronounced in this after picture. But again it could just be from the top she's wearing.
Miami plastic surgeon Dr. Michael Salzhauer thinks she got plastic surgery, though. Here's what he had to say,
"Kate Upton does appear to have breast implants as revealed by the very distinct and sharp transition from her full cleavage to her chest. Her breast augmentation fits her frame well and balances out her proportions."
Look at the next gallery picture to see the difference from right before she gained super stardom!